The present invention relates to an apparatus for measuring chromatic dispersion characteristic in a single mode optical fiber for optical communication.
The light in the optical fiber is propagated in the fiber at the speed of about 5 .mu.sec/km but chromatic dispersion occurs due to differences of propagation speeds in each of wavelengths. Therefore, the optical pulse signal of small duration expands in the side of output end deforming the waveform and results in the influence on the transmission of optical signal. Accordingly, it is necessary to previously measure the chromatic dispersion characteristic of the optical fiber to be used for the optical communication.
The U.S. Pat. No. 4,710,022 has proposed a method for measuring indirectly such chromatic dispersion characteristic.
As a direct method, the pulse delaying method has also been proposed and described in the following references,
(1) L. G. Cohen & C. Lin "A universal fiber-optic (UFO) measurement system based on a near-IR Raman Laser" IEEE J. Quantum Electron., QE-14, pp 855-859 (1985);
(2) T. Kanada & D. L. Franzen "Optical waveform measurement by optical sampling with a mode-locked laser dodes" Opt.Lett., 11, pp 4.about.6(1986);
(3) T. Kanada & D. L. Franzen "Single-mode fiber dispersion measurement using optical sampling with a mode-locked laser diodes", Opt. Lett., 11, pp 330.about.332 (1986).
However, these pulse delaying methods have problems in accuracy of measurement and size of apparatus.